1. Field of the Invention
The present invention pertains to a capture block assembly for use in preventing a shackle attached to a wire rope lifting assembly from being removed from said wire rope assembly without removal or destruction of said capture block assembly.
2. Brief Description of the Prior Art
Riggings of various types are commonly used in industrial applications, including, but not limited to, oil and gas well drilling, mining operations, the nuclear energy industry, and many others. In several of these applications, safety is a paramount concern, as such rigging equipment can be used for heavy overhead lifting; dropping or imprecise placement of such heavy loads can cause injury or death to personnel or property. Such heavy overhead lifting is often also dynamic in nature, frequently requiring heavy equipment to be lifted and moved using a pivoting crane.
In many such industrial rigging applications, wire rope is used with additional rigging hardware to form a sling assembly. Frequently, such wire rope sling assemblies include wire rope fittings, as well as termination hardware, which secure the ends of the wire rope together and prevent fraying. Often, such wire rope sling assemblies terminate in a loop, with a loose end of said loop being secured back onto the main wire rope body. A fitting or hardware (such as, for example, a clamp, a clip, a socket, and/or a swaged fitting) is typically used to secure said loose end back to said main wire rope body.
A thimble member is commonly used to preserve the natural shape of such a wire rope loop, particularly when exposed to loading. Such a thimble member provides a rigid surface along at least the inner surface of such a loop, and serves to prevent wire rope loops from bending too tightly when loaded. The thimble member prevents pinching and abrading of an inner surface of such a wire rope loop.
In many instances, shackles or other means can be used to connect the individual lines of a sling assembly to pad-eyes, lift lugs or other connection points of a load to be lifted. In conventional lifting applications utilizing existing shackle assemblies, a substantially U-shaped shackle having a mouth or opening is passed through the loop or eye of a sling or lifting cable. Thereafter, a bolt is threaded through aligned bores in said shackle and an opening in a lift lug or pad eye of a load to be lifted. Such shackles provide quick and efficient means for attaching a sling, cable, or other lifting device to a load to be lifted.
Said wire rope sling assemblies are often used in heavy duty lifting operations and, thus, can be placed under great loading stress and tension when in use. As a result, a component of said wire rope slings can sometimes fail or suffer damage during use, and users may replace individual components with spare parts from other sling assemblies. In many cases, said sling assemblies can be outfitted with cheaper or lower quality components, thereby compromising the overall integrity and lifting capacity of the wire rope sling assembly. In addition to being unsafe, this practice can subject a manufacturer and/or user of such a wire rope sling assembly to liability in the event of a failure.
National and international standards require that each component of wire rope sling assembly, including the shackles, be traceable to a record which can disclose information about the component, including, but not limited to, a material type, heat treatment, and a manufacturer of the individual components. If at least one shackle is changed or replaced without authorization, then a traceable record is no longer complete and accurate. It is therefore advantageous to incorporate a means whereby a shackle cannot be removed and replaced without permanent indication of such action.
Conventional means for capturing a shackle within a thimble member of a sling assembly involve welding on said thimble member. Such welding must be performed prior to assembly of the wire rope loop about the thimble. As such, the means for capturing the shackle must be performed during assembly of the wire rope sling. Moreover, it is not advisable or safe to perform welding on a thimble member after assembly of a wire rope sling assembly because the heat from the welding operations will be transferred through the thimble and into the wire rope, thereby changing the strength properties of said wire rope.
Thus, there remains a need for an improved wire rope sling assembly and components of said assembly that prevent unauthorized swapping or interchanging of shackle members between sling assemblies in the field. The improved sling assembly should permit capturing of a shackle within a loop thimble after a wire rope sling has been manufactured or assembled. Moreover, a shackle should be capable of being captured within a sling assembly loop thimble without requiring welding on said thimble.